Disclosed is a bio illuminance measuring apparatus including a circadian lambda filter passing external light along according to a circadian rhythm sensitivity curve, a visual lambda filter passing the external light along according to a visual sensitivity curve, a photo sensing portion sensing and converting the external light, which has passed through the circadian lambda filter, into a circadian wavelength signal and sensing and converting the external light, which has passed through the visual lambda filter, into a visual wavelength signal, and an illuminance calculating portion which calculates a ratio between the circadian wavelength signal and the visual wavelength signal, calculates a circadian action factor by applying the ratio between the circadian wavelength signal and the visual wavelength signal to a circadian action function which varies according to the visual wavelength signal, and calculates a bio illuminance value of the external light on the basis of the circadian action factor.